LIMITER_O block

Short summary

Name	`LIMITER_O`
→POU type	→function block
Category	Standard (non-safe), ControlEnh
Conform to →IEC-standard	not defined in IEC-standard
Graphical interface
Available since	version 1.47.0 (for Neuron Power Engineer) - initial variant version 3.8.0 (for library `Standard (non-safe)`): block moved in this library

Functionality

This block represents a hysteresis controller that switches abruptly between two states.

The block sets the value of the variable OUT to 1, if the value of the variable IN exceeds the value of L. The variable OUT is set to 0, if the value of IN falls below the value of L less the hysteresis H. Otherwise OUT keeps its value.
If a negative value is set for H, the value 0 is used for the hysteresis.

Restrictions

The following restrictions apply to the usage of overloadable function block instances:

The declaration is limited to local variables.
The usage as array base type is not allowed.
The usage as structure element is not allowed.
Instance data cannot be displayed in the Values of Variables view.

In-/outputs

	Identifier	→Data type	Description
Inputs:	`IN`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT` or `LINT` (corresponds to →generic data type `ANY_NUM`)	input
	L	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT` or `LINT` (corresponds to →generic data type `ANY_NUM`)	limit
	H	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT` or `LINT` (corresponds to →generic data type `ANY_NUM`)	hysteresis
Outputs:	`OUT`	`USINT`	`1` if `IN` exceeds the value of `L` `0` if `IN` falls below the value of (`L - H`)

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

See:

"Blocks for safe logic" whether this block is supported for developing safety-relevant applications.
"Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic.

Example for usage within ST-editor

FUNCTION_BLOCK ExampleLimiterO

VAR

        iLimiterO : LIMITER_O;

        limit : INT := 10;

        hysteresis : INT := 5;

        okOut1, okOut2, okOut3, okOut4 : BOOL := TRUE;

    END_VAR

    /* IN is below L => OUT keeps initial value of 0 */

    iLimiterO(IN := 10, L := limit, H := hysteresis);

    okOut1 := iLimiterO.OUT = 0;

    /* IN exceeds L => OUT changes its value to 1 */

    iLimiterO(IN := 11, L := limit, H := hysteresis);

    okOut2 := iLimiterO.OUT = 1;

    /* IN is between (L - H) and L => OUT keeps its value 1 */

    iLimiterO(IN := 6, L := limit, H := hysteresis);

    okOut3 := iLimiterO.OUT = 1;

    /* IN is below or equal (L - H) => OUT changes its value back to 0 */

    iLimiterO(IN := 5, L := limit, H := hysteresis);

    okOut4 := iLimiterO.OUT = 0;

    ENO := AND(okOut1, okOut2, okOut3, okOut4);

END_FUNCTION_BLOCK

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.